Nightsoil Kami
The 6/4 body is the tell. Where most Soulshift creatures were small, fragile bodies happy to die and rebuy something, this green beater trades up: large enough to demand a removal spell or a profitable block, and when it falls, it hands back a Spirit costing five or less. The 5-value threshold is generous by the keyword's standards, reaching nearly the entire tribe rather than the cheap dorks the lower numbers grabbed. That combination resolves a real tension in the Spirit graveyard engine: the small soulshifters chain among themselves but rarely threaten anyone, while a finisher-sized body that also feeds the chain has to justify its toughness against its recursion. Here the four toughness is the cost of admission, fragile enough that the death trigger feels earned rather than free. It plays as both the deck's clock and its safety net, the creature you are content to send into a bad attack because the value comes back when it dies. The reach of Soulshift 5 means it almost always has a worthwhile target waiting, making it the rare member of the cycle that wants to die and is hard to kill profitably at the same time.
